How to Manage Pests

Pests in Gardens and Landscapes

Bacterial ring rot—Clavibacter michiganensis
pv. sepedonicus

In some potato varieties bunchy or rosetted terminal leaves may appear on young plants. Terminals appear darker green than the rest of the plant. Foliar symptoms of bacterial ring rot generally appear at midseason or later. Yellow areas develop on leaf margins or between veins and later turn brown, giving the leaves a burned appearance. The leaflet margin rolls up and becomes necrotic. Plants with advanced symptoms show vascular discoloration and milky, viscous bacteria may be forced from cut stems. In tubers the rot begins as a brown necrosis in the vascular ring and progresses to the surface. Cracks may appear on surfaces of tubers, which are frequently nothing more than hollow shells.

Life cycle

Solutions

Use only certified seed tubers, rotate out of potatoes for at least 1 year, and follow strict sanitation procedures when cutting seed. Periodically disinfect cutting tools in a 1% solution of calcium hypochlorite.

Yellowing and burning of foliage
Yellowing and burning of foliage

Ring rot in tuber
Ring rot in tuber

Cracks on surface
Cracks on surface


Statewide IPM Program, Agriculture and Natural Resources, University of California
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Agriculture and Natural Resources, University of California

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